You want to display these tables on the screen? This means that you need to read all files one by one, load them into JSON object, extract the values from them, and only then you will be able to build the table. If a folder contains many files, this can take a lot of time.
You can put some of the information into the file name. Something like "Map_2000x1000_Forest_355objects.JSON"
And when user clicks this file, you can read it and display additional information - sprites locations and so on.